Disk record groove indicator



g- 9, 1932- J. c; CROWLEY 7 1,871,259

DISK RECORD GROOVE. INDICATOR Filegl Jan. 22. 1931 /N VE N TOR J. c. CRO WL E) 4 T TORNEY Patented Aug. 9, 1932 UNITED STATES, PATENT OFFICE JOHN G. CROWLEY, OF NEW YORK, N. Y., ASSIGNOR ELECTRICAL RESEARCH PROD- 'UGTS INCL, OF NEW YORK, N. Y.,

A ooaronnrron or DELAWARE DISK RECORD GROOVE INDICATOR Application filed January 22,1931. Serial No. 510,424.

This invention relates to disk record groove indicators which may be used with sound reproducers such as are employed 1n disk type phonographic devices.

Occasionally, reproducers are displaced from their grooves by accidental causes arising from a sudden jar or vibration of the record-supporting member or of the reproducer itself. To secure continuity of reproduction, it is imperative that the reproducer be returned to the groove from which it was displaced, and unless some indicating meansis used, this cannot be accomplished readily. i

The object of this invention is to provide a simple groove indicator which will indicate the exact groove through which a normally operated stylus should be passing, one of the features of the indicator being ameans for locating the reproducer stylus over the groove indicated.

The object of this invention is accomplished through the use of an auxiliary stylus and arm having a low moment of inertia as compared with that of the reproducer. This auxiliary stylus is located as near as possible to the reproducer stylus and has no'function other than to ride in the groove.

In order to set the reproducer into the proper groove as indicated by the auxiliary stylus, guides are provided on the auxiliary stylus arm which fit over the reproducer arm when it is not in operation, and are disengaged when it is in use.

These and other novel features will be apparent from the accompanying drawing and description thereof.

Fig. 1 is an elevation of the reproducer and indicator in playing position; Fig. 2 is the corresponding plan view; and Fig. 3 is a section on line 33 of Fig. 1 through the guides or locating saddle.

In Fig. 1, 10 is a reproducer and 11 the indicator with 12 and 13 their respective styluses, both tracking in the same groove of the record 14. The reproducer shown is of the standard type although this invention may be adapted equally well to other forms.

terial so as to reduce to a minimum its mass and moment of inertia with respect to the pivot 15 for horizontal motion and pivot 20 for vertical motion. This latter supports a saddle 21 which is free to rotate about pivot-2O through an angle of approximately 30, thereby permitting relative vertical. movement between the reproducer 10 and indicator 11. The stylus holder of the indicator is not fastened directly to the indicator arm but to a spring 16 which is so tensioned as to absorb the greater part of the vibrations of the stylus. This lowers its impedance and lessens the wear on the record?- The operation of the indicator is as ifol lows:

Both reproducer and indicator are normally madetomove laterally across the record by the pressure of the walls of the groove upon their respective styluses. Since both track in the same groove it isevident that any abrupt change in direction of the groove will manifest itself almost simultaneously in both. The masses associated with. the styluses, however, are unequal and the pressures required to produce an acceleration suflicient to keep both Styluses in the groove will be in direct proportlon to the masses. The only source of these pressures is the groove itself and the pressures obtainable from the groove are dependent upon its shape. This 1s very nearly constant and for a given sized stylus and groove there is a' limit to the pressure which is available.- Ifthe pressure required by the stylus is less than this limit, the stylus will remain in the groove; if on the other g hand the pressure required is greater than the limiting pressure the stylus will not be accelerated sufiiciently and in consequence will leave the groove.

The indicator is so designed that for the majority of disturbing conditions the pressure available will be ample to give it the required acceleration. The groove may change its direction or the entire record may be moved by a sudden jar which, in eifect, is equivalent to achange in the direction of the groove itself, but the indicator will follow its motion so long as this limiting pressure is not exceeded. The reproducer, not possessing the lightness and low moment of the stylus, the entire combination the indicator which has remained in the groove and raised until it en ages the guides 19, 19 at which point the sty us of the reproducer is exactly over the groove desired. It is then dropped into the groove.

Since the indicator tracks in the same groove as the reproducer, the latter can alsobe placed in its proper groove by simply noting the position of the indicator stylus and then tracing back along the groove to the reproducer stylus.

In starting the reproducer on the record the reproducer is lifted up in the usual manner, the indicator being lifted with it. The guides definitely fix the position of the indicator relative to the reproducer.- The indicator is then set into the desired oove and the reproducer dropped, falling ree of the guides and into the groove occupied by the indicator. The two remain in the same groove until some disturbing forcemanifests itself. At such time the reproducer will in all probability leave its groove, to be returned in the manner outlined above.

The form of the indicator arm as shown is but one of a number possible, the only restriction in this direction being a proper clearance between the reproducer and indicator arms while the indicator is tracking in its groove so that when the reproducer jumps its groove the two will not touch.

What is claimed is:

1. The combination with a sound reproducer and a groove type record of a groove indicator taking its position from the grooves on the record and used to indicate the correct groove on the record for the sound reproducer needle at any time during the playing of the record.

2. A groove indicating device comprising a free and universally pivoted arm, a stylus and a flexible member joiningl the arm and aving a small mass and moment of inertia with respect to its point of support so that it res onds readily when acted upon by a sudden orce.

3. The combination with a sound reproducer and a groove type record of a groove in-- for locating the reproducer over the groove occupied by the stylus.

In witness whereof, I hereunto subscribe my name this 16th da of January, 1931.

. JO N C. CROWLEY.

dicator having a low moment of inertia with respect to its point of support, com rised of an arm, a stylus and a flexible mem er 'oining the arm and stylus, said indicator ta ing its position from the grooves on the record and used to indicate the correct groove on the record for the sound reproducer needle at any time during the playing of the record.

4. The combination with asound reproducer adapted to be used with groove type rec- 

